Support for reverse iterators

tstl/include/iterator.hpp

@@ -21,6 +21,44 @@ size_t distance(Iterator it, Iterator end){
     return end - it;
 }
 
+template< typename Iterator>
+struct reverse_iterator {
+    using iterator_type   = Iterator;
+    using value_type      = typename std::iterator_traits<Iterator>::value_type;
+    using difference_type = typename std::iterator_traits<Iterator>::difference_type;
+    using pointer         = typename std::iterator_traits<Iterator>::pointer;
+    using reference       = typename std::iterator_traits<Iterator>::reference;
+
+    reverse_iterator(Iterator it) : it(it) {
+        //Nothing else
+    }
+
+    reference operator*(){
+        return *it;
+    }
+
+    reverse_iterator& operator++(){
+        --it;
+        return *this;
+    }
+
+    reverse_iterator& operator--(){
+        ++it;
+        return *this;
+    }
+
+    bool operator==(const reverse_iterator& rhs){
+        return it == rhs.it;
+    }
+
+    bool operator!=(const reverse_iterator& rhs){
+        return it != rhs.it;
+    }
+
+private:
+    iterator_type it;
+};
+
 template< typename Container >
 struct back_insert_iterator {
     using container_type = Container;

tstl/include/type_traits.hpp

@@ -15,12 +15,18 @@ namespace std {
 
 template <typename T>
 struct iterator_traits {
-    using value_type = typename T::value_type;
+    using value_type      = typename T::value_type;
+    using reference       = typename T::reference;
+    using pointer         = typename T::pointer;
+    using difference_type = typename T::difference_type;
 };
 
 template <typename T>
 struct iterator_traits <T*> {
-    using value_type = T;
+    using value_type      = T;
+    using reference       = T&;
+    using pointer         = T*;
+    using difference_type = size_t;
 };
 
 template<class T>

tstl/include/vector.hpp

@@ -21,11 +21,14 @@ namespace std {
 template<typename T>
 class vector {
 public:
-    typedef T                       value_type;
+    typedef T value_type;
-    typedef value_type*             pointer_type;
+    typedef value_type* pointer_type;
-    typedef size_t                  size_type;
+    typedef size_t size_type;
-    typedef value_type*             iterator;
+    typedef value_type* iterator;
-    typedef const value_type*       const_iterator;
+    typedef const value_type* const_iterator;
+
+    using reverse_iterator       = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
 private:
     T* data;
@@ -258,6 +261,24 @@ public:
         return const_iterator(&data[_size]);
     }
 
+    //Iterators
+
+    reverse_iterator rbegin(){
+        return iterator(&data[_size] - 1);
+    }
+
+    constexpr const_reverse_iterator rbegin() const {
+        return const_iterator(&data[_size - 1]);
+    }
+
+    reverse_iterator rend(){
+        return reverse_iterator(&data[-1]);
+    }
+
+    constexpr const_reverse_iterator rend() const {
+        return const_reverse_iterator(&data[-1]);
+    }
+
     // Relational operators
 
     bool operator==(const vector& rhs) const {

tstl/test_suite/vector.cpp

@@ -108,6 +108,39 @@ void test_push_front(){
     check(*a.begin() == 99);
 }
 
+void test_reverse_iterator(){
+    std::vector<int> a{1, 0, 0, 2, 3, 4};
+
+    auto it = a.rbegin();
+    auto end = a.rend();
+
+    check(it != end, "Invalid reverse iterator");
+    check(*it == 4, "Invalid reverse iterator");
+
+    ++it;
+    check(it != end, "Invalid reverse iterator");
+    check(*it == 3, "Invalid reverse iterator");
+
+    ++it;
+    check(it != end, "Invalid reverse iterator");
+    check(*it == 2, "Invalid reverse iterator");
+
+    ++it;
+    check(it != end, "Invalid reverse iterator");
+    check(*it == 0, "Invalid reverse iterator");
+
+    ++it;
+    check(it != end, "Invalid reverse iterator");
+    check(*it == 0, "Invalid reverse iterator");
+
+    ++it;
+    check(it != end, "Invalid reverse iterator");
+    check(*it == 1, "Invalid reverse iterator");
+
+    ++it;
+    check(it == end, "Invalid reverse iterator");
+}
+
 } //end of anonymous namespace
 
 void vector_tests(){
@@ -117,4 +150,5 @@ void vector_tests(){
     test_erase_remove();
     test_erase_remove_if();
     test_push_front();
+    test_reverse_iterator();
 }